Question

a)5x+y=-1
3x+4y=13

b)x-y=4
-2x+3y=-6

c)x+3y=34
2x-y=-2


d)x+y=60
5x-y=210

Answer 1

Resposta:

a) {5x + y = -1 y = -1 -5x

{3x + 4y = 13

3x + 4(-1 - 5x) = 13

3x -20x - 4 = 13

-17x = 13 + 4

-17x = 17

x = 17 / -17

x = -1

y = -1 -5 . (-1)

y= -1 + 5

y = 4

b) {x - y = 4 -y = 4 - x

{-2x + 3y = -6

-2x + 3(-4 + x) = -6

-2x -12 +3x = -6

x = -6 + 12

x = 6

-y = 4 - 6

-y = -2 .(-1)

y = 2

c) {x + 3y = 34 x = 34 - 3y

{2x - y = -2

2(34 - 3y) - y = -2

68 - 6y - y = -2

-7y = -2 - 68

-7y = -70

y = -70 / -7

y = 10

x = 34 - 3 . 10

x = 34 - 30

x = 4

d) {x + y = 60 x = 60 - y

{5x - y =210

5(60 - y) - y = 210

360 - 5y - y = 210

-6y = 210 - 360

-6y = -150 .(-1)

6y = 150

y = 150 / 6

y = 25

x = 60 - 25

x = 35